With the wide spread of mobile devices, the demands for secondary batteries have rapidly increased. Lithium ion secondary batteries having changeability in high energy density design cover most of the secondary battery market. The lithium ion secondary battery as a consumable part can be charged and discharged about 500 times and has a lifecycle of about six months to two years. Since a used lithium ion secondary battery includes a large amount of valuable metals such as lithium (Li) and cobalt (Co), and thus, the used lithium ion secondary batteries are recyclable resources having large economic values. By breaking the used lithium ion secondary battery for recycling, coarse grain including mainly aluminum (Al), gold (Au), copper (Cu), plastic, and the like and fine grain including mainly lithium, cobalt, nickel (Ni), manganese (Mn), and the like can be obtained. Korea is the world's second-largest consuming country for cathode material as a main constituent of the lithium ion secondary battery. Since a most amount of the cathode materials in Korea is dependent on import, recycling of the cathode materials by using the wasted battery has greatly drawn national interest. As a method of recycling the cathode materials, there is a solvent extraction method of dissolving the aforementioned fine grain of the wasted battery in a solvent and separating the fine grain with an extracting solution, and recovering highly-valuable cobalt and nickel among metals constituting the cathode materials. As a representative solvent extraction method, there is an extraction method using phosphoric acid series solvent. However, the extraction method using the phosphoric acid series solvent has problems of environmental pollution caused by the phosphoric acid series solvent, environmental pollution caused by manganese sulfate waste liquid containing manganese, copper, aluminum, calcium (Ca), sodium (Na), or the like discarded in the extraction process, and enormous cost for treating these materials. However, since the manganese sulfate waste liquid contains manganese sulfate, the manganese sulfate waste liquid may be good recyclable resources. If the manganese sulfate as a manganese oxide has a high purity, the manganese sulfate can be immediately used as a cathode material of the lithium ion secondary battery. However, most amount of the manganese sulfate used for manufacturing the secondary battery is also dependent on import. Therefore, if the manganese sulfate existing in the manganese sulfate waste liquid discarded in the wasted battery recycling process is recycled, the effects are expected in that a cost of treating waste water of the manganese sulfate waste liquid is expected to be saved and import substitution effect for the manganese sulfate is expected.
Patent Documents and reference documents disclosed in the specification are incorporated into the specification by reference to the same degree that the documents are individually and clearly specified.
Patent Document 1: Korean Patent No. 10-1542747